Actually, Tesla passed Toyota a month ago. Now passed Toyota, GM, Ford combined!
GM $36.9B + Ford $24.6B + $Toyota 175B = $236.5B total market cap
Tesla total market cap at the moment $246B!
But that is all a little misleading, because you add debt burden back into these legacy companies to get enterprise value (EV) and Toyota still has the highest EV at $313B. Tesla has very little debt and an EV of $231B at the moment. On that basis, Toyota is still the most valued company for now.
So, let's say there is a 100% buyout of Toyota, the stock would have to be bought plus Toyota debt must be paid off or assumed, less cash on hand.